Psychophysical experiments at UCSD will be undertaken with the principal aim of investigating brain processes underlying perception. The experiments include (1) studies of the minimally distinct border, (2) color scaling by a naming procedure, and (3) transient dichoptic masking. Human subjects will be used in all of this work. Electrophysiological experiments to be done in Dr. William Baron's laboratory at the Stanford Research Institute will be concerned with (1) measurements of rod saturation at the photoreceptor stage, (2) measurements of light distribution in the primate eye, and (3) studies of area effects that reveal interactions among primate photoreceptors. Cynomolgus macaque monkeys will be used in this work. The overall aim of the project is to explore the first and last stages of visual information processing in an attempt to reduce the scope of what remains to be explained in between.